Cationic electrodeposition coating is a coating method performed by immersing the article to be coated in cationic electrodeposition coating composition as a cathode and applying voltage to it. This method can apply a coating to details even if an article to be coated has a complicated shape. In addition, the method can be performed automatically and continuously. Thus, it is widely used practically as the undercoating method for an article to be coated having a large and complicated shape such as the car body of an automobile in particular. Furthermore, the electrodeposition coating can provide a high corrosion resistance to an article to be coated, and is excellent in the protective effect of the article to be coated.
Cationic electrodeposition coating composition is generally obtained by emulsifying or dispersing an aminated resin, a blocked isocyanate curing agent and a pigment in water. Cationic electrodeposition coating composition can form a film by conduction, it is necessary to use water as a solvent, thus, cationic electrodeposition coating composition contains a large amount of water.
In Japan, cationic electrodeposition coating composition is usually prepared by transporting an emulsion for the electrodeposition coating prepared in a paint company to a coating field, and by mixing the emulsion with a pigment dispersion paste and the like in the coating field. However, the above-mentioned emulsion for the electrodeposition coating contains a solvent composed mainly of water. Thus, when transporting it, since most of a transportation weight is water, it is necessary to enlarge transportation equipment, and a transportation cost was expensive. In addition, in order to store or transport the electrodeposition coating in an emulsion state, a strict temperature control was required to ensure emulsion stability. In order to reduce the inconvenience of a cost at the time of the transportation as described-above, it is conceivable to concentrate the emulsion solution. However, the concentration procedure may provide a viscosity rise, thus, the stability of the emulsion may be impaired, and an extra concentration cost may be required.
In addition, when an emulsion for the electrodeposition coating prepared in a domestic is transported to a domestic and international coating field, it is necessary a marine transportation by ships or tankers and/or a land transportation by trains/trucks. Also in this case, it is necessary to transport an emulsion containing large amounts of water as mentioned above with a temperature control, thus, a size and complexity of transportation equipment cannot be avoided, and also it is greatly reflected in a transportation cost. Therefore, an efficiency of transportation is required.
Japanese Patent Kokai Publication No. 2010-43189 (Patent Literature 1) discloses a replenishing coating composition containing a high concentration resin to be replenished to cationic electrodeposition coating composition. This technique is intended to improve the techniques to replenish the film-forming components using a replenishing coating, for a decrease of a film-forming component of cationic electrodeposition coating composition when use it. Also, this technique is intended to change a two-packed type of a replenishing coating into a one-packed type of it. Although this prior art also relates to a transportation point, this prior art does not relate to transportation of an emulsion for the electrodeposition coating, but relate to a replenishing coating. In addition, the replenishing coating also essentially contains a large amount of water.
Japanese Patent Kokai Publication No. 2012-092293 (Patent Literature 2) discloses a pigment dispersed paste of specific formulations. In paragraph [0002] of Patent Literature 2, as problems when transporting it to a coating equipment in overseas, it is described a technology which increases a storage stability of the pigment dispersed paste, since a pigment dispersed paste placed in a drum is in a non-stirring state. This technology does not relate to a transportation of an emulsion for a cationic electrodeposition coating composition, but relates a pigment dispersed paste.
[Patent Literature 1] JP-A-2010-43189
[Patent Literature 2] JP-A-2012-092293